1 //===- ConstantPools.cpp - ConstantPool class --*- C++ -*---------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the ConstantPool and  AssemblerConstantPools classes.
11 //
12 //===----------------------------------------------------------------------===//
13 #include "llvm/ADT/MapVector.h"
14 #include "llvm/MC/ConstantPools.h"
15 #include "llvm/MC/MCContext.h"
16 #include "llvm/MC/MCExpr.h"
17 #include "llvm/MC/MCStreamer.h"
18 
19 using namespace llvm;
20 //
21 // ConstantPool implementation
22 //
23 // Emit the contents of the constant pool using the provided streamer.
24 void ConstantPool::emitEntries(MCStreamer &Streamer) {
25   if (Entries.empty())
26     return;
27   Streamer.EmitDataRegion(MCDR_DataRegion);
28   for (const ConstantPoolEntry &Entry : Entries) {
29     Streamer.EmitCodeAlignment(Entry.Size); // align naturally
30     Streamer.EmitLabel(Entry.Label);
31     Streamer.EmitValue(Entry.Value, Entry.Size, Entry.Loc);
32   }
33   Streamer.EmitDataRegion(MCDR_DataRegionEnd);
34   Entries.clear();
35 }
36 
37 const MCExpr *ConstantPool::addEntry(const MCExpr *Value, MCContext &Context,
38                                      unsigned Size, SMLoc Loc) {
39   const MCConstantExpr *C = dyn_cast<MCConstantExpr>(Value);
40 
41   // Check if there is existing entry for the same constant. If so, reuse it.
42   auto Itr = C ? CachedEntries.find(C->getValue()) : CachedEntries.end();
43   if (Itr != CachedEntries.end())
44     return Itr->second;
45 
46   MCSymbol *CPEntryLabel = Context.createTempSymbol();
47 
48   Entries.push_back(ConstantPoolEntry(CPEntryLabel, Value, Size, Loc));
49   const auto SymRef = MCSymbolRefExpr::create(CPEntryLabel, Context);
50   if (C)
51     CachedEntries[C->getValue()] = SymRef;
52   return SymRef;
53 }
54 
55 bool ConstantPool::empty() { return Entries.empty(); }
56 
57 void ConstantPool::clearCache() {
58   CachedEntries.clear();
59 }
60 
61 //
62 // AssemblerConstantPools implementation
63 //
64 ConstantPool *AssemblerConstantPools::getConstantPool(MCSection *Section) {
65   ConstantPoolMapTy::iterator CP = ConstantPools.find(Section);
66   if (CP == ConstantPools.end())
67     return nullptr;
68 
69   return &CP->second;
70 }
71 
72 ConstantPool &
73 AssemblerConstantPools::getOrCreateConstantPool(MCSection *Section) {
74   return ConstantPools[Section];
75 }
76 
77 static void emitConstantPool(MCStreamer &Streamer, MCSection *Section,
78                              ConstantPool &CP) {
79   if (!CP.empty()) {
80     Streamer.SwitchSection(Section);
81     CP.emitEntries(Streamer);
82   }
83 }
84 
85 void AssemblerConstantPools::emitAll(MCStreamer &Streamer) {
86   // Dump contents of assembler constant pools.
87   for (auto &CPI : ConstantPools) {
88     MCSection *Section = CPI.first;
89     ConstantPool &CP = CPI.second;
90 
91     emitConstantPool(Streamer, Section, CP);
92   }
93 }
94 
95 void AssemblerConstantPools::emitForCurrentSection(MCStreamer &Streamer) {
96   MCSection *Section = Streamer.getCurrentSectionOnly();
97   if (ConstantPool *CP = getConstantPool(Section)) {
98     emitConstantPool(Streamer, Section, *CP);
99   }
100 }
101 
102 void AssemblerConstantPools::clearCacheForCurrentSection(MCStreamer &Streamer) {
103   MCSection *Section = Streamer.getCurrentSectionOnly();
104   if (ConstantPool *CP = getConstantPool(Section)) {
105     CP->clearCache();
106   }
107 }
108 
109 const MCExpr *AssemblerConstantPools::addEntry(MCStreamer &Streamer,
110                                                const MCExpr *Expr,
111                                                unsigned Size, SMLoc Loc) {
112   MCSection *Section = Streamer.getCurrentSectionOnly();
113   return getOrCreateConstantPool(Section).addEntry(Expr, Streamer.getContext(),
114                                                    Size, Loc);
115 }
116